Investigation of unsteady conjugate heat transfer for a radial turbine with impingement cooling

Abstract

For radial flow turbines, raising the temperature before the volute is also an important means of improving their thermal efficiency. As with axial flow turbines, excessive thermal load requires the application of cooling technology. In the study, impingement cooling technology was applied to a radial turbine, and the cooling effect of the turbine was investigated using conjugated heat transfer (CHT) simulations and experiments. The results showed that some of the coolant moved down into the back-disc heat shield cavity and impinged onto the back-disc. Most of the coolant eventually flowed into the rotor flow passage and stayed close to the blade suction side. The blade leading-edge shroud was the worst cooled area, but some temperature reduction was achieved. An experimental investigation was conducted with a high-speed infrared camera at much-reduced turbine speeds of 5000 and 10,000 rpm. The experimental results confirmed the numerical findings, and it was also found that cooling becomes more effective with the increase of turbine speed and of coolant relative mass flow. A 30°C reduction of blade leading-edge temperature was achieved with 3% relative coolant mass flow at 10,000 rpm.